The present invention relates generally to a roasting apparatus, and more particularly to a roasting apparatus for roasting nuts, cocoa beans, coffee beans, and other small food stuffs, the roasting apparatus comprising catalytic elements and a means of mixing the nuts or beans to significantly reduce or eliminate the unpleasant odors, gases and smoke generated in the roasting process.
Roasted coffee beans lose their freshness very quickly. However, raw green coffee beans remain fresh almost indefinitely. When raw green coffee beans are roasted to a dark brown color, the roasting gives off a very foul, pungent smell and generates smoke that would be considered unpleasant in a household environment. Most prior art household coffee bean roasting apparatus have several disadvantages, such as roasting only a small amount of coffee beans, non-uniformity in roasting, and the emission of foul odors and smoke during the roasting process. Perhaps the greatest challenge to controlling these odors is the common use of high air velocities of hot air to heat and mix the beans in prior art devices. The prior art household coffee bean roasting apparatus that use the high air velocities of hot air to generate large volumes of exhaust gases in order to xe2x80x9cfloatxe2x80x9d and circulate the beans in a similar manner to hot air popcorn poppers in order to uniformly roast the coffee beans. The coffee bean roasting apparatus of the present invention roasts a larger amount of coffee beans than the prior art, roasts the beans more uniformly, and eliminates the roasting odors and smoke associated with the roasting process.
It has long been known by commercial coffee roasting professionals and coffee enthusiasts that the smell of roasting raw coffee beans is typically regarded as unpleasant. Especially in the latter stages of roasting, the beans exude substantial quantities of oils and particulate matter as a byproduct of caramelization and pyrolysis, which can impart an unpleasant odor during roasting. Many attempts have been made to reduce or control these odors and waste gases by way of filtration, burning, and/or venting.
While some of these attempts have proved successful for commercial roasting operations, efforts to control exhaust gases in a household environment have been unsuccessful.
The filtration of exhaust gases is a problem. Given the minute particle size of coffee bean roasting exhaust gases, very fine filtration media is required to materially reduce escaping gases. Filters meeting or exceeding the Department of Energy""s (DOE) High-Efficient Particulate Air (HEPA) standards are required. These filters require considerable pressurization for the exhaust gases to pass through. Therefore, the filters would require loud, powerful and expensive blowers to meet the pressurization requirements. Also, since these relatively large, expensive filters cannot be cleaned or reused, the high cost of regularly replacing these filters seriously limits their attractiveness to the average household consumer.
The combustion of exhaust gases is also a problem. Open flame combustion of exhaust gases is commonly used in commercial roasting operations. In this method, natural gas is forced into a combustion chamber where it is ignited and mixed with the roasting exhaust gases before being released into the atmosphere. Although this method is effective and popular in commercial roasting operations, it is clearly impractical for the home coffee bean roasting enthusiast. Catalytic elements similar to those found in automotive pollution control equipment have also been used in commercial coffee roasting operations, but are less popular than the open flame method, primarily due to the high cost of the precious metals used to coat the catalytic elements. The prior art household coffee bean roasters that use high air velocities of hot air generate large volumes of exhaust gases that would require very large catalytic elements to adequately burn off the exhaust gases, making them impractical for household use.
The venting of exhaust gases is a further problem. Historically this method has been the most common. However, given increasing concerns over air quality, most municipalities no longer permit commercial coffee bean roasting operations to release waste gases into the atmosphere without pretreatment. Most household coffee bean roasting apparatus have long used this method as their only option. Consequently, many coffee bean roasting devices are only used outdoors or near an open window. Needless to say, in many parts of the country roasting coffee beans near an open window or outdoors is not feasible for much of the year. Many manufacturers advise against using their product indoors unless adequate venting is available. However, many homes do not have adequate venting available. Indeed, experience has shown that most consumer kitchen vents cannot keep up with the exhaust gases generated from the typical home coffee bean roasting apparatus.
Therefore, it would be desirable to provide a roasting apparatus that roasts a larger amount of coffee beans than most prior art household devices, roasts the beans uniformly, and significantly reduces or eliminates the roasting odors and smoke associated with the roasting process.
In view of the problems associated with prior art roasting appliances, it is an object of the present invention to provide a roasting apparatus, which overcomes the drawbacks of the prior art. In particular, it is an object of the present invention to provide a roasting apparatus that significantly reduces or eliminates the unpleasant odors associated with in-home coffee bean roasting.
It is another object of the present invention to provide a roasting apparatus that provides an effective means of mixing the beans during roasting by using an auger to greatly reduce the amount of heated air required for the roasting process, while at the same time greatly reducing the amount of odiferous exhaust gases generated.
It is a further object of the present invention to provide a roasting apparatus that directs is exhaust gases from the roasting process past a collection member to capture the chaff and dust carried in the exhaust gases as they flow around the perimeter of the collection member.
It is yet another object of the present invention is to provide a roasting apparatus having a filter across the exhaust gas airflow to prevent dust and chaff from escaping the roasting chamber and clogging the catalytic elements.
It is another object of the present invention to provide a roasting apparatus that channels the exhaust gases through a second heating element to elevate the exhaust gas temperature to over 700 degrees Fahrenheit to provide proper operating temperatures to the catalytic elements.
It is a further object of the present invention to provide a roasting apparatus that channels the exhaust gases through catalytic elements to burn off particulates, smoke, oils or other materials contained in the exhaust gases.
Additionally, it is an object of the present invention to provide a roasting apparatus that mixes the heated exhaust gases with room temperature air prior to expelling the combined air stream from the roasting apparatus, thereby preventing heat damage to the operator or other objects in the environment. These and other objects are met by the roasting apparatus of the present invention.
The present invention is directed to a roasting apparatus, such as a coffee bean roasting apparatus, for roasting granular material, such as nuts, cocoa beans and coffee beans. The roasting apparatus includes a base, a motor and afterburner assembly attached to the top of the base on one side thereof, a roasting assembly attached to the top of the base on the other side thereof, and a top cover assembly removably attached to the tops of the motor and afterburner assembly and the roasting assembly.
Preferably mounted within the base of the roasting apparatus is a blower assembly coupled to an electric motor for providing airflow through the roasting assembly, a drive assembly also coupled to the motor for driving an auger positioned within a roasting chamber of the roasting assembly, a roasting chamber heating assembly for heating the airflow from the blower assembly prior to entering the roasting chamber, and a digital control assembly for controlling and programming operation of the roasting apparatus.
The motor and afterburner assembly preferably includes the electric motor for driving the auger, and for driving a blower within the blower assembly and for driving a fan positioned at the opposite end of the motor from the blower for providing airflow through the afterburner assembly. The afterburner assembly preferably includes an afterburner intake member for receiving exhaust gases from the roasting assembly, a catalyst heating element for heating the exhaust gases before entering a catalyst, and a catalyst heat shield surrounding the catalyst.
The roasting assembly preferably includes a roasting chamber heating assembly positioned within the base for heating the airflow from the blower assembly prior to entering the roasting chamber, the removable roasting chamber and auger, and a chaff collection assembly positioned on top of the roasting chamber.
The removable top cover assembly preferably includes an open channel formed between an upper heat shield and a lower heat shield for allowing exhaust gases and smoke to flow from the roasting chamber into the afterburner assembly. The top cover assembly further includes a filter for filtering out dust and chaff from the exhaust gases emanating from the roasting chamber and depositing the chaff into the chaff collection assembly on top of the roasting chamber.
During a roasting cycle of the roasting apparatus, the motor driven blower assembly supplies room temperature air to the roasting chamber heating assembly, where the air is heated to a suitable roasting temperature by an electrical heating element. Upon leaving the heating assembly, the heated air is forced upward through the porous base of the roasting chamber. As the heated air passes between the coffee beans, heat is transferred from the air to the beans thereby raising bean temperature to the desired degree of roast.
Even heating of the beans is assured by the constant agitation and exchange of the beans by the rotating auger. A gentle radius formed into the base of the roasting chamber constantly feeds a supply of beans to the base of the auger, where the beans are lifted to the top of the column of beans. Upon reaching the top of the column of beans, the beans lifted by the auger are permitted to spill out onto the top of the bean column where they are subsequently returned to the bottom of the roasting chamber by the force of gravity.
After the heated air passes through the column of beans and reaches the top of the roasting chamber, it is forced to flow around a chaff collection member; a drop in air pressure causes most of the dust and chaff to fall into the chaff collection member. Beyond the chaff collection member the smoke and exhaust gases pass through a filter, which captures any remaining dust or chaff. The exhaust gases then pass through the open channel in the top cover assembly to the afterburner assembly and into a second heating element (the catalyst heating element) which raises the exhaust gas temperature to a minimum of 700 degrees Fahrenheit before it passes through a catalyst. Heating of these gases to a minimum of 700 degrees Fahrenheit enables the catalyst to properly react with the particulate matter contained in the exhaust gases. As the exhaust gases pass through the narrow channels of the catalyst, the materials on the surface of the catalyst, such as platinum and/or palladium react with the gases thereby breaking down the particulates and gases to their odorless components. As the exhaust gases escape the catalyst, the heated air stream is mixed with room temperature air from the fan and subsequently vented to the environment.
When the beans reach the desired level of roast, the roasting cycle ends, and a cool down cycle begins. A controller in the digital control assembly shuts off the roasting heating element and increases the speed of the motor, thereby increasing the RPM of the blower, fan and auger and causing the beans to be cooled. The second heating element used to heat the exhaust gases entering the afterburner assembly and catalyst remains on until the exhaust gases escaping the roasting chamber are cooled and no longer contain odor causing smoke and particulates. When the beans have become cooled, the motor and catalyst heating element are turned off, and the roasting chamber with the roasted beans may be removed and emptied.
Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof.